Vehicle security systems are widely used to deter vehicle theft, prevent theft of valuables from a vehicle, deter vandalism, and to protect vehicle owners and occupants. A typical automobile security system, for example, includes a central processor or controller connected to a plurality of vehicle sensors. The sensors, for example, may detect opening of the trunk, hood, doors, windows, and also movement of the vehicle or within the vehicle. Ultrasonic and microwave motion detectors, vibration sensors, sound discriminators, differential pressure sensors, and switches may also used as sensors. In addition, radar sensors may be used to monitor the area proximate the vehicle. The controller also typically operates to give an alarm indication in the event of triggering of a vehicle sensor. The alarm indication may typically be a flashing of the lights and/or the sounding of the vehicle horn or a siren. In addition, the vehicle fuel supply and/or ignition power may be selectively disabled based upon an alarm condition.
A typical security system also includes a receiver associated with the controller that cooperates with one or more remote transmitters typically carried by the user as disclosed, for example, in U.S. Pat. No. 4,383,242 to Sassover et al. The remote transmitter may be used to arm and disarm the controller in the vehicle or provide other remote control features from a predetermined range outside the vehicle.
As disclosed in U.S. Pat. No. 5,049,867 to Stouffer and U.S. Pat. No. 5,146,215 to Drori, the controller may include features to store and compare unique codes associated with a plurality of remote transmitters, each remote transmitter having its own unique code initially programmed therein. Transmitter codes may be added or deleted from the controller corresponding to the number of remote transmitters desired by the user. Unfortunately, a would-be thief gaining access to the controller may readily enter the programming or learn mode and install the code of an unauthorized remote transmitter. The owner would thus be unaware of such activity, until the thief returns with the unauthorized remote transmitter to disarm the security system and steal the vehicle.
A vehicle security system sold by Clifford under the trademark INTELLIGUARD 900 includes random code encryption of messages sent by a remote transmitter. Accordingly, a would-be thief who records a transmitted code cannot simply retransmit the same code to gain access to the vehicle. Rather, a different code is sent with each transmission of the remote transmitter. In other words, the security system is somewhat resistant to being disarmed by a code grabber or a code scanner. However, the security system simply ignores signals other than properly encrypted signals.
In addition, a typical security system includes a valet switch, for example, to permit the system to enter the so-called valet mode, wherein the alarm functions are disabled. The valet mode permits authorized use the vehicle by a technician or valet without concern for the vehicle alarm inadvertently being triggered. Typically, the valet switch is positioned away from plain view in the vehicle. A vehicle security system sold under the mark VIPER included the ability to enter the valet mode via a remote transmitter. The remote activation disabled security features of the system, but left convenience features still operable.